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knoevenagel condensation wikipedia jump to content main menu main menu move to sidebar hide navigation main page contents current events random article about wikipedia contact us contribute help learn to edit community portal recent changes upload file special pages search search appearance donate create account log in personal tools donate create account log in contents move to sidebar hide top 1 doebner modification 2 examples and applications 3 weiss cook reaction 4 see also 5 references toggle the table of contents knoevenagel condensation 22 languages العربية azərbaycanca català čeština deutsch español فارسی suomi français հայերեն bahasa indonesia italiano 日本語 nederlands polski português română русский slovenčina svenska українська 中文 edit links article talk english read edit view history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikimedia commons wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia organic chemical reaction knoevenagel condensation named after emil knoevenagel reaction type coupling reaction identifiers organic chemistry portal knoevenagel condensation rsc ontology id rxno 0000044 in organic chemistry the knoevenagel condensation pronounced ˈknøːvənaːɡl̩ reaction is a type of chemical reaction named after german chemist emil knoevenagel it is a modification of the aldol condensation 1 2 a knoevenagel condensation is a nucleophilic addition of an active hydrogen compound to a carbonyl group followed by a dehydration reaction in which a molecule of water is eliminated hence condensation the product is often an α β unsaturated ketone a conjugated enone general knoevenagel layout in this reaction the carbonyl group is an aldehyde or a ketone the catalyst is usually a weakly basic amine the active hydrogen component has the forms 3 z ch 2 z or z chr z for instance diethyl malonate meldrum s acid ethyl acetoacetate or malonic acid or cyanoacetic acid 1 z chrr for instance nitromethane where z is an electron withdrawing group z must be powerful enough to facilitate deprotonation to the enolate ion even with a mild base using a strong base in this reaction would induce self condensation of the aldehyde or ketone the hantzsch pyridine synthesis the gewald reaction and the feist benary furan synthesis all contain a knoevenagel reaction step the reaction also led to the discovery of cs gas doebner modification edit the doebner modification of the knoevenagel condensation acrolein and malonic acid react in pyridine to give trans 2 4 pentadienoic acid with the loss of carbon dioxide the doebner modification of the knoevenagel condensation entails the use of pyridine as a solvent with at least one of the withdrawing groups on the nucleophile is a carboxylic acid for example with malonic acid under these conditions the condensation is accompanied by decarboxylation 4 for example the reaction of acrolein and malonic acid in pyridine gives trans 2 4 entadienoic acid with one carboxylic acid group and not two 5 sorbic acid can be prepared similarly by replacing acrolein with crotonaldehyde 6 examples and applications edit a knoevenagel condensation is demonstrated in the reaction of 2 methoxybenzaldehyde 1 with the thiobarbituric acid 2 in ethanol using piperidine as a base 7 the resulting enone 3 is a charge transfer complex molecule a knoevenagel condensation the knoevenagel condensation is a key step in the commercial production of the antimalarial drug lumefantrine 8 final step in lumefantrine synthesis the initial reaction product is a 50 50 mixture of e and z isomers but because both isomers equilibrate rapidly around their common hydroxyl precursor the more stable z isomer can eventually be obtained a multicomponent reaction featuring a knoevenagel condensation is demonstrated in this more synthesis with cyclohexanone malononitrile and 3 amino 1 2 4 triazole 9 knoevenagel tandem application weiss cook reaction edit the weiss cook reaction consists in the synthesis of cis bicyclo 3 3 0 octane 3 7 dione employing an acetonedicarboxylic acid ester and a diacyl 1 2 ketone the mechanism operates in the same way as the knoevenagel condensation 10 see also edit malonic ester synthesis nitroalkene iminocoumarin references edit 1 2 g jones 2004 the knoevenagel condensation organic reactions pp 204 599 doi 10 1002 0471264180 or015 02 isbn 0471264180 emil knoevenagel 1898 condensation von malonsäure mit aromatischen aldehyden durch ammoniak und amine condensation of malonic acid with aromatic aldehydes via ammonia and amines berichte der deutschen chemischen gesellschaft 31 3 2596 2619 doi 10 1002 cber 18980310308 smith michael b march jerry 2007 advanced organic chemistry reactions mechanisms and structure 6th ed new york wiley interscience p 1358 1363 isbn 978 0 471 72091 1 o doebner 1902 ueber die der sorbinsäure homologen ungesättigten säuren mit zwei doppelbindungen berichte der deutschen chemischen gesellschaft 35 1136 36 doi 10 1002 cber 190203501187 jessup peter j petty c bruce roos jan overman larry e 1979 1 n acylamino 1 3 dienes from 2 4 pentadienoic acids by the curtius rearrangement benzyl trans 1 3 butadiene 1 carbamate organic syntheses 59 1 doi 10 15227 orgsyn 059 0001 allen c f h vanallan j 1944 sorbic acid organic syntheses 24 92 doi 10 15227 orgsyn 024 0092 1 3 diethyl 5 2 methoxybenzylidene 2 thioxodihydropyrimidine 4 6 1h 5h dione abdullah mohamed asiria khaled ahmed alamrya abraham f jalboutb suhong zhang molbank 2004 m359 archived 9 july 2011 at the wayback machine publication an improved manufacturing process for the antimalaria drug coartem part ii ulrich beutler peter c fuenfschilling and andreas steinkemper org process res dev 2007 11 3 pp 341 45 article doi 10 1021 op060244p mild and ecofriendly tandem synthesis of 1 2 4 triazolo 4 3 a pyrimidines in aqueous medium arkivoc 2007 06 2251bp anshu dandia pritima sarawgi kapil arya and sarita khaturia link weiss u edwards j m 1968 a one step synthesis of ketonic compounds of the pentalane 3 3 3 and 4 3 3 propellane series tetrahedron letters 9 47 4885 doi 10 1016 s0040 4039 00 72784 5 retrieved from https en wikipedia org w index php title knoevenagel_condensation oldid 1372283262 categories condensation reactions name reactions carbon carbon bond forming reactions hidden categories articles with short description short description is different from wikidata use dmy dates from january 2024 pages with german ipa webarchive template wayback links this page was last edited on 31 august 2026 at 03 22 utc page was rendered with parsoid text is available under the creative commons attribution sharealike 4 0 license additional terms may apply by using this site you agree to the terms of use and privacy policy wikipedia is 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